The trend of technological development in magnetic recording using magnetic heads advances to high frequency and high density recording. To make denser record, the recording medium used in magnetic tape, magnetic disc and the like should be of material having high magnetic coercive force (Hc), but the high magnetic coercive force should accompany with high saturation magnetism of magnetic heads corresponding to the high magnetic coercive force. It is possible to record only when the saturation magnetism of magnetic heads is 5 to 8 times higher than the magnetic coercive force of the medium. Iron oxide family tape having a magnetic coercive force of 500-800 Oe is used currently with ferrite family magnetic heads having a saturation magnetism of 5000 Gauss.
However, because recording with magnetic heads employing ferrite is not easy on media used in 8 mm video camera and digital audio tape recorders have a magnetic coercive force of 1500 Oe, metal in gap (MIG) heads have been developed which are magnetic heads having a thin film of metal of high saturation magentism between the head gap.
Shown in FIG. 1 is a perspective view of a conventional MIG head, wherein 1a and 1b ere core halves to make one core together, 2 is bonding glass and 3 is ferromagnetic film.
Sendust alloy (Fe-Al-Si) having good thermal stability and strong corrosion resistance is mostly used for the ferromagnetic film 3, and the forming of the film is carried out by sputtering. The bonding glass 2 bonding the core haves 1a and 1b is material of high wear resistance and high corrosion resistance, and requires heating at 500.degree.-700.degree. C. to melt in bonding the halves 1a and 1b.
However, the heating causes the problem of the occurence of inter-diffusion between the surfaces of the ferrite blocks 1a and 1b and the ferromagnetic film 3, which results to generate pseudo-gap noise, an impediment in recording/reproduction. And the metal magnetic film 3 tends to deteriorate it/high temperature resulting in a drop of the output due to reaction with the glass 2. Consequently, it is current situation of magnetic head manufacture to employ metal magnetic film materials having good high temperature properties though the magnetic properties are more or less low. It has not been possible to use materials having good magnetic properties but with low thermal stability.